This invention relates to frame structures and more particularly to the structure of corners for such frames.
It has been common practice in the manufacture of aluminum window and door frames to use mitred joints which are either secured by welding or screws to support a piece joining the adjacent channels.
However, the weld joints and the screw joints have become expensive because of their high labour content.
They also have several individual shortcomings. The welded joints are difficult to maintain and the screw joints tend to loosen. With both types of joints, however, there has been the problem of strength. To provide strength, a relatively thick gauge of metal has to be provided to prevent warping.
The screw joints, if not countersunk, normally had to be provided on a surface of the window which if not visible, restricted the hinge movement, and if not hidden from view was exposed to the elements so that there was provided a further entry for the elements and deterioration of the structure.
Furthermore, the screw joints were not secure.